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Ratcheting behavior and dislocation evolution law of non-oriented electrical steel

  • Time of issue:2020-10-20 02:22

(Summary description)The 30WGP1600 non-oriented electrical steel was subjected to a system cycle test under uniaxial stress control, and the influence of average stress, stress amplitude and peak stress on the ratchet behavior of the material was analyzed. The dislocation configuration during ratchet deformation was observed by TEM transmission electron microscope. The law of evolution reveals the nature of the deformation of electrical steel ratchets.    Under the action of cyclic stress, the structure produces an accumulation of irreversible deformation, namely the ratchet effect. The ratchet effect can cause structural parts to fail due to excessive size or fatigue deformation, bringing catastrophic consequences.

Ratcheting behavior and dislocation evolution law of non-oriented electrical steel

(Summary description)The 30WGP1600 non-oriented electrical steel was subjected to a system cycle test under uniaxial stress control, and the influence of average stress, stress amplitude and peak stress on the ratchet behavior of the material was analyzed. The dislocation configuration during ratchet deformation was observed by TEM transmission electron microscope. The law of evolution reveals the nature of the deformation of electrical steel ratchets.    Under the action of cyclic stress, the structure produces an accumulation of irreversible deformation, namely the ratchet effect. The ratchet effect can cause structural parts to fail due to excessive size or fatigue deformation, bringing catastrophic consequences.

  • Categories:Industry News
  • Author:
  • Origin:"Electrical Materials" Du Liying et al
  • Time of issue:2020-10-20 02:22
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  The 30WGP1600 non-oriented electrical steel was subjected to a system cycle test under uniaxial stress control, and the influence of average stress, stress amplitude and peak stress on the ratchet behavior of the material was analyzed. The dislocation configuration during ratchet deformation was observed by TEM transmission electron microscope. The law of evolution reveals the nature of the deformation of electrical steel ratchets.

  Under the action of cyclic stress, the structure produces an accumulation phenomenon of irreversible deformation, that is, the ratchet effect. The ratchet effect can cause structural parts to fail due to excessive size or fatigue deformation, bringing catastrophic consequences. For example, the rotor of an electric vehicle drive motor will deform ratchets under the action of centrifugal force. On the one hand, the ratchet deformation increases the probability of contact between the rotor and the stator, which leads to the failure of the motor; on the other hand, the irreversible plastic deformation deteriorates the magnetic performance of the motor, severely damages its function, and reduces the service life of the motor. Therefore, in order to optimize the motor structure and correct safety assessment, it is necessary to fully understand the ratchet deformation behavior of the non-oriented electrical steel for the rotor under high frequency and low stress in the design of the motor.

  In recent decades, a large number of experiments and theoretical studies have been conducted on the ratcheting effect of materials at home and abroad, but most of the studies on the ratcheting behavior of materials are low loading frequency, high applied stress (greater than the yield strength of the material), and the number of cycles Within thousands of cycles, there is still a lack of experimental understanding of the ratcheting behavior of materials under low stress (peak stress is less than or equal to the yield strength), high loading frequency, and hundreds of thousands of cycles, and the ratcheting behavior of non-oriented electrical steel is more researched. Rarely reported. Therefore, for 30WGP1600 non-oriented electrical steel, the evolution process of ratcheting strain of non-oriented electrical steel under low stress and high cycle cycles, and the influence of average stress, stress amplitude and peak stress on its ratcheting behavior are studied. System description and analysis The strain change process of the material under low stress and the evolution law of the dislocation structure are discussed.

  The ratcheting behavior of 30WGP1600 non-oriented electrical steel under low stress and high cycle cycles is studied, the ratcheting behavior of electrical steel is analyzed, and the dislocation configuration evolution law during ratcheting deformation process is systematically studied, and the following main conclusions are drawn.

  (1) Regardless of how the stress amplitude and average stress change, the ratchet strain of electrical steel increases with the increase of the peak stress. Therefore, the peak stress is the dominant factor affecting the deformation of electrical steel ratchets.

  (2) When the applied peak stress is less than 300MPa, the ratchet deformation is almost not occurred, and the electrical steel is in the elastic deformation stage; when the peak stress is greater than 300MPa but less than 340MPa, the ratchet deformation of electrical steel is small, and the ratchet saturation state is reached at the beginning of the cycle; When the peak stress is greater than 340 MPa but less than or equal to the yield strength, the ratchet strain increase rate first increases and then decreases, and it can be stabilized after about 100,000 cycles.

  (3) When the peak stress is between 300 and 340 MPa, the dislocation density is low, and the dislocation configuration is mostly dislocation lines. When unloading in the reverse direction, the dislocation movement is easier and the deformation recoverability is good; when the peak stress At 340-400 MPa, multiple slip systems are easy to start, the dislocation density increases and the interaction is enhanced, the resistance of the dislocation movement increases, and the irreversibility of deformation increases. In this stage, the amount of ratchet deformation increases greatly.

  (4) When the peak stress is the yield strength, at the beginning of the cycle (that is, the first stage), the dislocation movement and multiplication speed is very fast, and the ratchet strain rate is also large; in the second stage of ratchet deformation, the dislocation configuration changes from low density The dislocation entanglement transforms to high-density dislocation walls and primary dislocation cells. Compared with the first stage, the dislocation multiplication rate is lower, and the ratchet strain rate is correspondingly reduced; in the third stage of ratchet deformation, the high-density dislocation group The state evolves to an incomplete dislocation cell structure, the cell structure is relatively stable, and the ratchet strain rate keeps increasing at a constant rate.

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